As far as ultrasonic probes of recent years are concerned, a variety of types have been hitherto developed. A conventional ultrasonic probe will be explained by using FIGS. 7 and 8. FIG. 7 is a drawing illustrating a configuration of a conventional ultrasonic probe. FIG. 8 is a view of the ultrasonic probe shown in FIG. 7 as seen from the direction of an arrow 101. As shown in FIG. 7, the ultrasonic probe is constituted to have a grip section 1 and an insert section 2, and the insert section 2 has a configuration including a tip section 3 that in turn includes a base section 3a. A motor 5, and a drive pulley 102 which is swingably or rotatably driven by the motor 5 are incorporated inside the grip section 1. Additionally, a wire drive mechanism 100 which transmits power to a swing pulley 7 by using a wire 8 transmitting the power by the swinging or rotation of the drive pulley 102, the swing pulley which swings around a rotation shaft 9 by the power resulting from the swinging or rotation of the drive pulley 102 transmitted through the wire 8, and an ultrasonic transducer unit 4 operated by the swinging of the swing pulley 7, are incorporated in the interior of the insert section 2. Moreover, as shown in FIG. 8, the ultrasonic probe includes a position angle sensor 103, which detects the position angle of the ultrasonic transducer unit 4. Such an ultrasonic probe is disclosed in Patent document 1 indicated below.    Patent document 1: Japanese Patent Application Publication No. 10(1998)-179588 (FIG. 3)
Nevertheless, in the ultrasonic probe disclosed in Patent document 1, there has been such a problem that the positional displacement occurs due to the slippage of wire 8 on the drive pulley 102 and the swing pulley 7 while swinging. Moreover, since a mechanism had not been included which adjusts the origin position angle of the ultrasonic transducer unit 4 in its swing operation when the wire 8 is attached to the drive pulley 102 and the swing pulley 7, there has been such a problem that a position angle sensor 103, which detects the position angle of the swing pulley 7 must have been incorporated. Furthermore, there has been a problem such that the wire 8 used became long.